The principal objective of this proposal is to develop a reproducible model for gonococcal arthritis in the dog. Pilot studies indicate that gonococcal endocarditis is an important prerequisite for the development of arthritis in this animal. By producing serum-resistant gonococci in vitro, an attempt will be made to increase the attack rate of arthritis, and possibly bypass the need for endocarditis as a predisposing lesion. Joint fluid paracentesis and synovial biopsies will be conducted sequentially to evaluate histopathologic, microbiologic, ultrastructural, and immunologic aspects of joint infection. The antigonococcal activity of serum synovial fluid, and phagocytes will be evaluated before, and at intervals during infection to determine whether resistance of gonococci to host defense mechanisms is enhanced during the course of infection. Various culture media will be evaluated in an attempt to improve the rate of bacteriologic diagnosis in experimental gonococcal arthritis.